Sesquialtera in the Colombian Bambuco: Perception and Estimation of Beat and Meter - Extended version.

Bambuco, one of the national rhythms of Colombia, is characterized by the presence of sesquialtera or the superposition of rhythmic elements from a simple and a compound meter. In this work, we analyze bambucos from three perspectives. First, we analyze the perception of beat and meter by asking 10 Colombian musicians to perform beat annotations in a dataset of bambucos. Results show great diversity in the annotations: a total of five metric alternatives (meters or combinations of meters) were found in the annotations, with each bambuco in the study being annotated in at least two different meters. To get a better understanding of which elements influence meter perception in bambucos, elements in three categories (composition, performance and audio production) were identified in our second study, and summarized for our bambuco dataset. In our third study, we use state-of-the-art computational tools for beat and meter analysis to extract beat positions. Given that the algorithms used in the analysis were designed to deal with the rhythmic regularity of a single meter, it is not surprising that tracking performance is not very high. However, a deeper analysis of the onset detection functions used for beat tracking indicates that there is enough information on the signal level to characterize the bi-metric behavior of bambuco. Our beat tracking analysis on bass tracks as well as our analysis of downbeat estimation indicate that while current computational tools cannot directly handle the bi-metric elements in bambuco, they provide valuable information that can be used for musicological analysis.